The present invention relates to safety devices for garage doors and the like. More particularly, the invention relates to improvements in safety devices which can be used in or with doors of the type wherein the panel or panels tend to assume a predetermined position in response to the action of gravity or another force which is normally counteracted by one or more springs, weights or the like.
Commonly owned German Pat. No. 33 00 331 discloses a safety device whose blocking or locking action is dependent upon centrifugal force. A horizontal shaft of the garage door carries a gear which rotates relative to a housing and relative to a casing. The casing is rotatable, within limits, with respect to the housing under the action of a coil spring tending to maintain the casing in an angular position in which the casing and the housing cooperate to prevent rotation of the gear relative to the housing, for example, in response to failure of one or more torsion springs which tend to rotate the shaft and the gear thereon to a position in which the coil spring is compressed. The housing and the casing have recesses which can receive portions of spherical blocking elements in the tooth spaces of the gear. The blocking elements can enter the recesses of the housing and the casing only when the coil spring is free to expand so that the blocking elements then prevent further rotation of the shaft and of the gear thereon relative to the housing.
The patented safety device has been found to be highly effective in actual use. However, its operation is dependent (at least to a certain degree) upon the action of centrifugal force which tends to propel the blocking elements from the respective tooth spaces of the gear. Furthermore, the patented safety device employs a reasonably large number of blocking elements which must orbit relative to the housing whenever the shaft for the gear is set in rotary motion. Such orbital movements of the blocking elements can generate some noise. Moreover, uncontrolled or unauthorized manipulation of the casing can result in disengagement of the blocking elements and in rapid discent of the garage door with attendant likelihood of damage to the door and injury to the person or persons standing nearby. PG,4